Dye developer



Patented July 16, 1946 DYE DEVELOPER George L. Armour, New York, N. Y.,assignor to American Aniline Products, 1110., New York, N. 1., acorporation of New York No Drawing. Application November 29, 1941,

l Serial No. 420,965 7 2 Claims.

This invention relates to dyeing processes as applied to rayon yarns andparticularly to cellulose acetate rayon and similar synthetic yarns. Itwill be understood, of course, in'using the term rayon I am using thisterm in the present generally accepted commercial use which includesboth cellulose acetate yarns, regenerated viscose yarns, and similarsynthetic yarns.

More particularly, it is concerned with developers that are used in thedyeing of cellulose acetate yarns.

Present day requirements call for speed in dyeing in order to save costand to meet demands for quick deliveries. In the dyeing processes as atpresent practised, the material is passed through a bath containing thedyestufi" for a period of two to two and a half hours, after which it isrinsed well and diazotized with sodium nitrite and muriatic acid for afurther 30-35 minutes cold, after which it is again rinsed well in coldwater and developed to its proper shade with beta hydroxy naphthoic acidwhich is run 30-35 minutes at 60 C.

The preparation of this developing bath, however, has always presentedconsiderable difliculties from a production standpoint. Beta hydroxynaphthoic acid is not water soluble and it has always been considerednecessary to combine it with certain alkalies such as caustic soda, am-

monia, or soda ash. This, indeed, renders it water soluble but at thesame time has brought it down to an alkaline condition in which it isunsuitable as a developer. The general practice has been to overcomethis alkalinity by the addition of certain acids such as acetic orformic acid. This is for the reason that the developer must be on theacid side at about a pH of to 6, in order to couple the developer withthe already diazotized dyestuff on the material. Assuming, for instance,that it is desired to produce a full black color on the material, if thedeveloper is not properly acidified, brownish blacks and various otherundesirable shades will result because of the improper coupling of thedeveloper.

The various steps required in rendering the developer suitable for itspurpose in the dyeing process are accompanied by numerous hazards. Chiefamong these are the following: In dissolving the developer beta hydroxynaphthoic acid with alkalies, it often happens that there may be left acertain amount of free alkali in the solution because of thecarelessness of the workmen car rying out the process, or for otherreasons. Furthermore, even with extreme care it is not always possibleto be sure of the proper pH, lot after lot, so as to produce consistentshades of black in each operation. It may be added also that even whenthe operations are carried out with the utmost care, there isconsiderable time consumed in observing certain precautions such as thetesting of the developing bath in order to determine its pH.

It is an object of the present invention to provide a method ofdeveloping the color in the dyeing operation that avoids all thesehazards which have been above enumerated.

Briefly, it is an object of the present invention to provide a method ofpreparing the beta hydroxy naphthoic acid developer without changing itsacid character. In other words, it is an object of the invention toprovide such a developing bath without incurring the various hazards dueto alkalizing the beta hydroxy naphthoic acid and then bringing it backto the acid side.

I have discovered that if beta hydroxy naphthoic acid is thoroughlymixed with sodium formate while both are in the dry state, and then hotwater at a temperature of about C. to C. added, with stirring, theresulting product becomes water soluble without being alkalized andwithout materially changing its pI-I. In other words, the developerwhich is a sodium salt of beta hydroxy naphthoic acid remains on theacid side and in the solution above indicated is immediately ready to beadded to the developing bath, and when so used the pH of the developingliquor is consistent and consequently produces consistent full shades ofthe desired color.

The following is a specific example of the use of the developer of thepresent invention: A dyestufi, such aspara-amino-benzene-azo-dihydroxyethylanilin in solution, is prepared andcellulose acetate rayon is introduced thereinto and allowed to remain inthe bath for about two to two and a half hours. This dyestuff is thendiazotized upon the material as before stated. A developer is thenprepared by adding to beta hydroxy naphthoic acid, sodium formate in thedry state. Hot water at a temperature of about 85 C. to 100 C. is thenadded with stirring. The reaction of the developer then proceedsaccording to the following equation:

This developer is then added to what is known as the developing bath.The cellulose acetate rayon having been previously treated as aboveindicated is then immersed in this developing bath at a temperature ofabout 35 C. to 40 C.

with sodium formate (I-ICOONA) which may be represented by the formula:CH6OH.COONA, a sodium salt of beta hydroxy naphthoic acid having a pH ofabout 5 to 6.

Having thus described my invention, what I claim is:

1. The method of preparing a developing bath for acetate rayon dyeswhich consists in adding sodium formate to beta hydroxy naphthoic acid,

both being in the form of dry powders; then adding water at atemperature of about 85 C. to 100 C. with stirring, thereby causing thesodium formate to react with the beta hydroxy naphthoic acid yieldingwater soluble reaction products to form a developing bath having a pH ofabout 5 to 6.

2. The method of developing colors'on acetate rayon that consists intreating dyed and diazotized acetate rayon by immersing it in a bathcontaining a solution formed by adding beta hydroxy naphthoic acid tosodium formate and hot water, said immersion taking place in saidsolution at a temperature of C. to 40 C., then raising the temperatureof the bath to about C. and maintaining this temperature for aboutthirty minutes, then rinsing the rayon with fresh water and extractingand drying it.

GEORGE L. ARMOUR.

